U.S. patent number 5,606,477 [Application Number 08/515,936] was granted by the patent office on 1997-02-25 for viscoelastically damped slider suspension system.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to A. David Erpelding, Oscar J. Ruiz.
United States Patent |
5,606,477 |
Erpelding , et al. |
February 25, 1997 |
Viscoelastically damped slider suspension system
Abstract
A slider suspension system for use in a magnetic recording disk
file comprised of a laminated suspension positioned between an
actuator arm and a read/write slider. The laminate is comprised of
a copper alloy conductor layer, a polyimide dielectric layer and a
stainless steel stiffener layer. A pattern of land areas are etched
in the conductor layer and act as constraining areas for the
viscoelastic dielectric layer. The constrained layer/constraining
layer configuration damps vibrations existing in the suspension
system.
Inventors: |
Erpelding; A. David (San Jose,
CA), Ruiz; Oscar J. (San Jose, CA) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
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Family
ID: |
22797008 |
Appl.
No.: |
08/515,936 |
Filed: |
August 16, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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213913 |
Mar 15, 1994 |
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Current U.S.
Class: |
360/244.3;
G9B/5.153; G9B/5.154 |
Current CPC
Class: |
G11B
5/4833 (20130101); G11B 5/486 (20130101); H05K
1/0271 (20130101); H05K 1/09 (20130101); H05K
1/05 (20130101); H05K 2201/2045 (20130101); H05K
2201/0154 (20130101); H05K 2201/0355 (20130101); H05K
2201/09781 (20130101); H05K 1/056 (20130101) |
Current International
Class: |
H05K
1/02 (20060101); G11B 5/48 (20060101); H05K
1/09 (20060101); H05K 1/05 (20060101); G11B
005/48 () |
Field of
Search: |
;360/103,104 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0487914 |
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Jun 1992 |
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EP |
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0568257 |
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Nov 1993 |
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EP |
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53-30310 |
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Mar 1978 |
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JP |
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01-248372 |
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Mar 1989 |
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JP |
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01189083 |
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Jul 1989 |
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JP |
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02-218078 |
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Aug 1990 |
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JP |
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03-91173 |
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Apr 1991 |
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JP |
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03-278382 |
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Dec 1991 |
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JP |
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4219618 |
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Aug 1992 |
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JP |
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5-36048 |
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Feb 1993 |
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JP |
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2193833 |
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Feb 1988 |
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GB |
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WO92/13345 |
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Aug 1992 |
|
WO |
|
Other References
E M. Kerwin, "Damping of Flexural Waves by a Constrained
Viscoelastic Layer," The Journal of the Acoustical Society of
America, vol. 31, pp. 952-962 (1959). .
Anonymous disclosure, "Circuitized Suspension Flexure-Foliage for
Disk Drives, " Published in Research Disclosure, No. 339, Kenneth
Mason Publications Ltd, England (Jul. 1992). .
Cooper et al., "Constrained Layer Damper Spring Assemblies, " IBM
Technical Disclosure Bulletin, vol. 33, No. 8, pp. 373-374 (Jan.
1991). .
C. E. Yeack-Scranton, "PVF.sub.2 Resonance Damping For Magnetic
Recording, " IBM Technical Disclosure Bulletin, vol. 28, No. 12,
pp. 5611-5613 (May 1986). .
J. H. Nayak, "Auxiliary Mass Damping of DIsk-File Sliders, " IBM
Technical Disclosure Bulletin, vol. 26, No. 6, pp. 2922-2923 (Nov.
1983). .
R. Plunkett and C. T. Lee, "Length Optimization for Constrained
Viscoelastic Layer Damping, " The Journal of the Acoustical Society
of America, vol. 48, pp. 150-161 (1970). .
F. Maseeh and S. Senturia, "Viscoelasticity and Creep Recovery of
Polyimide Thin Films, " VLSI Memo 90-600, MIT (Jun. 1990)..
|
Primary Examiner: Levy; Stuart S.
Assistant Examiner: Klimowicz; William J.
Attorney, Agent or Firm: Pagel; Donald J.
Parent Case Text
This is a continuation of Ser. No. 08/213,913, filed Mar. 15, 1994
now abandoned.
Claims
What is claimed is:
1. A suspension system for supporting a data transducer
comprising:
a laminated section comprised of a first layer comprised of a
metal, a second layer comprised of a dielectric material and
positioned over the first layer, and a third layer comprised of an
electrically conducting material and positioned over the second
layer;
a first land area formed on the laminated section consisting of a
four-sided region of the third layer, the first land area having a
width c measured between two opposite sides of the first land area,
the first land area constraining a first region of the second layer
positioned underneath the first land area so that shearing occurs
in the first region in response to deformation in the second
layer;
a second land area formed on the laminated section consisting of a
four-sided region of the third layer, the second land area having a
width d measured between two opposite sides of the second land
area, the second land area constraining a second region of the
second layer positioned underneath the second land area so that
shearing occurs in the second region in response to deformation in
the second layer;
a third land area formed on the laminated section consisting of a
four-sided region of the third layer, the third land area having a
width e measured between two opposite sides of the third land area,
the third land area constraining a third region of the second layer
positioned underneath the third land area so that shearing occurs
in the third region in response to deformation in the second layer,
with the width c, the width d and the width e all lying parallel to
a straight line which intersects the first land area, the second
land area and the third land area;
a first channel formed on the laminated section completely
surrounding the first land area and isolating the first land area
from any other part of the third layer so as to enhance the ability
of the first land area to constrain the first region, the first
channel extending through the third layer and exposing the second
layer;
a second channel formed on the laminated section completely
surrounding the second land area and isolating the second land area
from any other part of the third layer so as to enhance the ability
of the second land area to constrain the second region, the second
channel extending through the third layer and exposing the second
layer; and
a third channel formed on the laminated section completely
surrounding the third land area and isolating the third land area
from any other part of the third layer so as to enhance the ability
of the third land area to constrain the third region, the third
channel extending through the third layer and exposing the second
layer.
2. The suspension system of claim 1 wherein the width c, the width
d and the width e are each in the range of approximately 0.3 to 0.8
millimeters.
3. The suspension system of claim 1 wherein the width c, the width
d and the width e are each in the range of approximately 0.1 to 0.8
millimeters.
4. The suspension system of claim 1 wherein the first layer
comprises a stainless steel, the second layer comprises a polyimide
and the third layer comprises a copper alloy.
5. The suspension system of claim 1 wherein the first, second and
third land areas each comprise a solid region of the third
layer.
6. A suspension system for supporting a read/write transducer in a
disk drive comprising:
a laminated section comprised of a first layer comprised of a
metal, a second layer comprised of a dielectric material and
positioned over the first layer, and a third layer comprised of an
electrically conducting material and positioned over the second
layer;
a first land area formed on the laminated section and comprising a
multisided region of the third layer surrounded on all sides by a
plurality of spaces that extend through the third layer and expose
the second layer, the first land area having a width c in the range
of 0.3 to 0.8 mm, the first land area constraining a first region
of the second layer positioned underneath the first land area so
that shearing occurs in the first region in response to deformation
in the second layer;
a second land area formed on the laminated section and comprising a
multisided region of the third layer surrounded on all sides by a
plurality of spaces that extend through the third layer and expose
the second layer, the second land area having a width d in the
range of 0.3 to 0.8 mm, the second land area constraining a second
region of the second layer positioned underneath the second land
area so that shearing occurs in the second region in response to
deformation in the second layer;
a third land area formed on the laminated section and comprising a
multisided region of the third layer surrounded on all sides by a
plurality of spaces that extend through the third layer and expose
the second layer, the third land area having a width e in the range
of 0.3 to 0.8 mm, the third land area constraining a third region
of the second layer positioned underneath the third land area so
that shearing occurs in the third region in response to deformation
in the second layer;
a first channel formed on the laminated section separating the
first land area and the second land area, the first channel
extending through the third layer and exposing the second
layer;
a second channel formed on the laminated section separating the
second land area and the third land area, the second channel
extending through the third layer and exposing the second layer,
the width d of the second land area extending from the first
channel to the second channel;
a third channel formed on the laminated section and positioned
adjacent to a first edge of the first land area, a first edge of
the second land area and a first edge of the third land area, the
third channel intersecting the first channel and the second channel
and extending through the third layer and exposing the second
layer;
a fourth channel formed on the laminated section and positioned
adjacent to a second edge of the first land area, a second edge of
the second land area and a second edge of the third land area, the
fourth channel intersecting the first channel and the second
channel and extending through the third layer and exposing the
second layer;
a fifth channel formed on the laminated section and separating the
first land area from any other part of the third layer, the fifth
channel extending through the third layer and exposing the second
layer, the width c of the first land area extending across the
first land area in a direction parallel to the width d; and
a sixth channel formed on the laminated section and separating the
third land area from any other part of the third layer, the sixth
channel extending through the third layer and exposing the second
layer, the width e of the third land area extending across the
third land area in a direction parallel to the width d.
7. The suspension system of claim 6 wherein the third layer is
comprised of a copper alloy, the second layer is comprised of a
polyimide and the first layer is comprised of a stainless
steel.
8. The suspension system of claim 6 wherein the fourth channel
extends along an outside edge of the laminated section.
9. The suspension system of claim 6 wherein the width c, the width
d and the width e are aligned parallel to an axis of a bending or
torisional mode.
10. The suspension system of claim 6 wherein the first, second and
third land areas each comprise a solid region of the third
layer.
11. A suspension system for supporting a read/write slider in a
disk drive comprising:
a laminated section comprised of a first layer comprised of a
metal, a second layer comprised of a dielectric material and
positioned over the first layer, and a third layer comprised of an
electrically conductive material and positioned over the second
layer;
a read/write slider attached to a first end of the laminated
section;
a first land area formed on the laminated section and comprising a
multisided region of the third layer surrounded on all sides by a
plurality of spaces that extend through the third layer and expose
the second layer, the first land area having a width c in the range
of 0.3 to 0.8 mm, the first land area constraining a first region
of the second layer positioned underneath the first land area so
that shearing occurs in the first region in response to deformation
in the second layer;
a second land area formed on the laminated section and comprising a
multisided region of the third layer surrounded on all sides by a
plurality of spaces that extend through the third layer and expose
the second layer, the second land area having a width d in the
range of 0.3 to 0.8 mm, the second land area constraining a second
region of the second layer positioned underneath the second land
area so that shearing occurs in the second region in response to
deformation in the second layer;
a third land area formed on the laminated section and comprising a
multisided region of the third layer surrounded on all sides by a
plurality of spaces that extend through the third layer and expose
the second layer, the third land area having a width e in the range
of 0.3 to 0.8 mm, the third land area constraining a third region
of the second layer positioned underneath the third land area so
that shearing occurs in the third region in response to deformation
in the second layer;
a first channel formed on the laminated section separating the
first land area and the second land area, the first channel
extending through the third layer and exposing the second
layer;
a second channel formed on the laminated section separating the
second land area and the third land area, the second channel
extending through the third layer and exposing the second layer,
the width d of the second land area extending from the first
channel to the second channel;
a third channel formed on the laminated section and positioned
adjacent to a first edge of the first land area, a first edge of
the second land area and a first edge of the third land area, the
third channel intersecting the first channel and the second channel
and extending through the third layer and exposing the second
layer;
a fourth channel formed on the laminated section and positioned
adjacent to a second edge of the first land area, a second edge of
the second land area and a second edge of the third land area, the
fourth channel intersecting the first channel and the second
channel and extending through the third layer and exposing the
second layer;
a fifth channel formed on the laminated section and separating the
first land area from any other part of the third layer, the fifth
channel extending through the third layer and exposing the second
layer, the width c of the first land area extending across the
first land area in a direction parallel to the width d; and
a sixth channel formed on the laminated section and separating the
third land area from any other part of the third layer, the sixth
channel extending through the third layer and exposing the second
layer, the width e of the third land area extending across the
third land area in a direction parallel to the width d.
12. A disk drive including the suspension system of claim 11
further comprising:
a data storage medium accessible by the read/write slider; and
an actuator connected to a second end of the laminated section for
moving the laminated section relative to the data storage
medium.
13. The suspension system of claim 11 wherein the first, second and
third land areas are four-sided regions.
14. The suspension system of claim 11 wherein the first layer
comprises a stainless steel, the second layer comprises a polyimide
and the third layer comprises a copper alloy.
15. The suspension system of claim 11 wherein the first, second and
third land areas each comprise a solid region of the third layer.
Description
TECHNICAL FIELD
The present invention relates to a suspension system for the slider
in a disk drive and more particularly to a laminated suspension
system having a pattern etched into one of the laminated layers for
creating constrained areas that facilitate damping of various
vibrational modes in the system.
BACKGROUND ART
Magnetic recording disk files that utilize a transducer mounted on
a slider for reading and/or writing data on at least one rotatable
disk are well-known in the art. In such systems, the slider is
typically attached to an actuator arm by a suspension system.
The use of laminated materials for constructing slider suspension
systems in magnetic disk files is also known in the art. For
example, Erpelding et al., in U.S. Pat. No. 4,996,623, issued Feb.
26, 1991, disclose a suspension system comprised of a sheet of
polyimide material sandwiched between two metal layers. Similarly,
Ainslie et al., in U.S. Pat. No. 4,761,699, issued Aug. 2, 1988,
disclose a slider attached to a laminated suspension.
It is known that vibration of the arm and suspension in disk drives
produces undesirable effects such as nonrepeatable runout of the
recording element on the slider. One known approach to reducing
such vibration is to incorporate a viscoelastic material into the
suspension system that supports the slider. For example, Pal et
al., in U.S. Pat. No. 4,760,478, issued Jul. 26, 1988, disclose a
magnetic head support arm having a layer of viscoelastic material
fixed to the load bearing member for damping vibrations in the
support arm.
In analyzing the problem of unwanted vibrations in generalized
systems, theoretical models have been developed for using a
constrained layer and a constraining layer to damp the vibrations.
These models indicate that the effectiveness of the overall damping
obtained depends on the stiffness of the constrained layer as well
as on its length. The appropriate length can be estimated in
several ways, and both analytical and experimental methods have
been used. For example, in a paper entitled "Damping of Flexural
Waves by a Constrained Viscoelastic Layer," The Journal of the
Acoustical Society of America, vol. 31 (1959), by E. M. Kerwin, the
effective length of the constrained layer is related to the
wavelength of bending waves.
In another paper, entitled "Length Optimization for Constrained
Viscoelastic Layer Damping," The Journal of the Acoustical Society
of America, vol. 48 (1970), by R. Plunkett and C. T. Lee, an
effective constraining layer length is determined for single and
multiple damping layers. In another paper, entitled
"Viscoelasticity and Creep Recovery of Polyimide Thin Films," VLSI
Memo 90-600, MIT (June 1990) by F. Maseeh and S. Senturia, the
viscoelastic properties of thin polyimide films are characterized
and measured.
None of the prior art discloses using the constrained
layer/constraining layer principles to solve the problem of
unwanted vibrations in slider suspensions for magnetic disk drives.
Furthermore, as the track density of information storage media,
like hard magnetic disks, increases, the need for slider suspension
systems that reduce vibrations to a minimum continues to grow in
importance.
SUMMARY OF THE PRESENT INVENTION
Briefly, the preferred embodiment of the present invention is a
slider suspension system for use in a magnetic recording disk file
that utilizes a constrained layer/constraining layer design to damp
vibrations existing in the suspension system. The system includes a
laminated suspension for attachment between the slider and the
actuator arm, comprised of a conductor layer, a dielectric layer
and a stiffener layer. The dielectric layer is comprised of a
material that exhibits some viscoelastic properties, like a
polyimide, and functions as the constrained layer to damp
vibrations arising in the stiffener layer. The conductor layer
includes a pattern of land areas that act as constraining areas for
the dielectric layer.
In an alternative embodiment of the present invention, a V-shaped
tongue is formed in the conductor layer and stiffener layer. The
tongue allows the polyimide dielectric layer to undergo stretching
and shear, thereby damping bending and torsional modes of vibration
experienced by the suspension system.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of a slider suspension system according to the
present invention;
FIG. 2 is a cross-sectional view of the slider suspension system
taken along the line 2--2 of FIG. 1;
FIG. 3 is a top view of an alternative embodiment of a slider
suspension system according to the present invention;
FIG. 4 is a cross-sectional view of the slider suspension system
taken along the line 4--4 of FIG. 3; and
FIG. 5 is a schematic diagram of a disk file that utilizes the
slider suspension system according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a top view of a slider suspension system 10. The system
10 has a slider portion 14, an arm portion 18 and a link portion 22
(also referred to as a load beam). A plurality of signal guard
lines 25 and electrical lines 26 are present on a surface 30 of the
system 10. Each electrical line 26 has a space 34 positioned along
each of its sides so as to prevent the electrical line 26 from
shorting out with an adjacent electrical line 26 or guard line 25.
Similarly, each signal guard line 25 has a space 34 positioned
along each of its sides so as to prevent the guard line 25 from
shorting out with an adjacent electrical line 26 or guard line 25.
The signal guard lines 25 function to carry unwanted electrical
signals to the ground circuit of the disk file. These unwanted
electrical signals are produced by stray electromagnetic fields
from the outside environment.
The portions 14, 18 and 22 designate regions of the system 10, but
the system 10 is formed from one continuous piece of laminated
material as is explained later with reference to FIG. 2.
The slider portion 14 is the part of the system 10 on which a
read/write slider 35 is mounted. The read/write slider includes a
transducer for reading and writing data on a medium such as a hard
magnetic disk. The electrical lines 26 form the electrical
connections for connecting the slider 35 to an external system as
is explained later with respect to FIG. 5.
The arm portion 18 is the part of the system 10 that is connected
to an actuator arm, such as the arm 136 shown in FIG. 5. Typically,
the arm portion 18 is attached to the actuator arm by bonding the
arm portion 18 to the actuator arm along the first layer 50 shown
in FIG. 2.
A pair of hinges 36 are provided between the arm portion 18 and the
link portion 22. Similarly, a hinge 37 is positioned at the end of
the link portion 22 adjacent to the slider portion 14.
The link portion 22 includes a plurality of land areas 38, a
plurality of spaces 40 and a plurality of spaces 41, positioned on
the surface 30 in a pattern referred to as a "zebra" pattern. Each
land area 38 is separated from each adjacent land area 38 by one of
the spaces 40. The spaces 41 border the land areas 38 along each
side of the land area 38 not surrounded by a space 40, so that each
land area 38 is completely surrounded by a combination of the
spaces 40 and 41.
The shape of the land areas 38 is not critical, but typically each
land area 38 is a multisided enclosed region. As is shown in FIG.
1, some of the sides of the land area 38 can be curved. Other
shapes such as circles, polygons, squares, rectangles and
trapezoids could also be used for the land areas 38.
A second set of land areas 43 and spaces 44 and 45 are positioned
about a centerline 46 which lies along the longitudinal axis of the
system 10. Each land area 43 is a multisided enclosed region that
is separated from each adjacent land area 43 by one of the spaces
44. The spaces 45 border the land areas 43 along each side of the
land area 43 not surrounded by a space 44, so that each land area
43 is completely surrounded by a combination of the spaces 44 and
45.
In the preferred embodiment, some of the land areas 38 (labelled
"a" in FIG. 1) are positioned about an axis 47 that passes near the
anchor site 36 and bisects two or more of the land areas 38(a).
Each of the land areas 38(a) are multisided regions that are
slightly curved about the axis 47 and are surrounded on all sides
by either the spaces 40 or the spaces 41. The land areas 38(a) have
a width "c" measured along a line that perpendicularly bisects
adjacent land areas 38 (i.e. in the direction of the axis 47).
Also, in the preferred embodiment one of the spaces 41 runs along
an edge 48 of the system 10. The spaces 40 intersect the space 41
that runs along the edge 48. An axis 49 runs through the two hinges
36 and is perpendicular to the centerline 46, and an axis 51 runs
through the hinge 37 perpendicular to the centerline 46.
FIG. 2 is a cross-sectional view of the slider suspension system 10
illustrating that the system 10 is a laminated structure comprised
of a first layer 50, a second layer 54 and a third layer 58. The
first layer 50 is positioned adjacent to one surface of the second
layer 54. The third layer 58 is positioned adjacent to a different
surface of the second layer 54 so that the second layer 54
separates the first layer 50 and the third layer 58, with the
layers 50, 54 and 58 all lying in planes that are parallel to each
other.
As can be seen in FIG. 2, the land areas 38 are regions of the
third layer 58 that are roughly rectangular in cross section, and
that are separated from each adjacent land area 38 by one of the
spaces 40. The spaces 40 extend down to the second layer 54 so that
the second layer 54 is exposed through the space 40.
Representative dimensions and compositions for the various elements
illustrated in FIGS. 1 and 2 are as follows: The spaces 40 and 44
have a width "b" of approximately 0.05 to 0.1 millimeters. The land
areas 38 and 43 have the width "c" of approximately 0.4
millimeters. The first layer 50 has a thickness "w" of
approximately 0.051 millimeters and comprises a rigid material such
as stainless steel. The second layer 54 has a thickness "x" of
approximately 0.006 millimeters and comprises a viscoelastic
dielectric material such as a polyimide. The third layer 58 has a
thickness "y" of approximately 0.0127 millimeters and comprises an
electrically conducting material such as a high strength beryllium
copper alloy.
It should be appreciated that the values listed above are dependent
on the particular pattern of the land areas 38 and 43, and spaces
40, 41, 44 and 45, and on the materials used in the layers 50, 54
and 58. For different systems, different values will need to be
determined.
The land areas 38 and 43, and the electrical lines 26 and signal
guard lines 25 are formed by etching the surface 30 using standard
metal etching techniques. For example, when the third layer 58
comprises beryllium copper, the layer 58 is etched with ferric
chloride. The etching process removes metal from specified regions,
thereby forming the spaces 34, 40, 41, 44 and 45 that define the
electrical lines 26, the signal guard lines 25 and the land areas
38 and 43.
With respect to the spaces 34, 40, 41, 44 and 45, metal from the
third layer 58 is completely removed by the etching process leaving
the second layer 54 exposed through the space 34, 40, 41, 44 or 45.
In practice, a typical chemical etching process will not form a
groove having the perfect rectangular shape illustrated in FIG. 2
for the spaces 40. Actual grooves formed by a chemical etching
process are slightly rounded or tapered as is well-known in the
art.
In the preferred embodiment, the first, second and third layers 50,
54 and 58 initially comprise a continuous sheet of laminated
material of beryllium copper/polyimide/stainless steel laminate. A
plurality of slider suspension systems 10 are then manufactured
from the sheet of laminate. The preparation of metal-polyimide film
laminates is described by St. Clair et al. in U.S. Pat. No.
4,543,295 (issued Sep. 24, 1985).
FIG. 3 is a top view of an alternative embodiment of a slider
suspension system 70. The system 70 has a slider portion 74, an arm
portion 78 and a link portion 82. A plurality of electrical lines
86 and signal guard lines 87 are present on a surface 90 of the
system 70. Each electrical line 86 is separated from each adjacent
electrical line or guard line 87 by a space 94 so as to prevent the
electrical line 86 from shorting out with an adjacent electrical
line 86 or guard line 87. Similarly, each signal guard line 87 has
a space 94 positioned along each of its sides so as to prevent the
guard line 87 from shorting out with an adjacent electrical line 86
or guard line 87. A V-shaped tongue 98, having a length "L," is
formed on the surface 90 by cutting a V-shaped channel 102 around
the perimeter of the tongue 98.
FIG. 4 is a cross-sectional view of the slider suspension system 70
illustrating that the system 70 is a laminated structure comprised
of a first layer 106, a second layer 110 and a third layer 114. The
first layer 106 is positioned on one surface of the second layer
110. The third layer 114 is positioned on a different surface of
the second layer 110 so that the second layer 110 separates the
first layer 106 and the third layer 114, with the layers 106, 110
and 114 all lying in planes that are parallel to each other.
As can be seen in FIG. 4, the channel 102 is a region around the
tongue 98 where the third layer 114 has been removed so that the
second layer 110 is exposed. Also, a portion of the first layer 106
underneath the channel 102 is removed exposing the second layer 110
and forming a tapered channel 118. Thus, the second layer 110 is
exposed on both sides of the channel 102. The channel 118 follows
the shape of the channel 102 all around the perimeter of the tongue
98 and so also has the V-shape of the channel 102.
Representative dimensions and compositions for the various elements
illustrated in FIGS. 3 and 4 are as follows: The channel 102 has a
width "f" of approximately 0.4 millimeters and the length "L" is
approximately 6.3 millimeters. The layers 106, 110 and 114 are
analogous to the layers 50, 54 and 58 and have the same dimensions
and compositions so that the first layer 106 has a thickness "g" of
approximately 0.051 millimeters and comprises a rigid material such
as stainless steel. The second layer 110 has a thickness "h" of
approximately 0.006 millimeters and comprises a viscoelastic
dielectric material such as a polyimide. And the third layer 114
has a thickness "k" of approximately 0.0127 millimeters and
comprises an electrically conducting material such as a beryllium
copper alloy.
It should be appreciated that the values listed above are dependent
on the particular pattern of the tongue 98 and channels 102 and
118, and on the materials used in the layers 106, 110 and 114. For
different systems, different values will need to be determined.
The tongue 98 and the electrical lines 86 and guard lines 87, are
formed by etching the surface 90 using standard metal etching
techniques as was discussed previously with respect to the
suspension system 10. The etching process removes metal from
specified regions, thereby forming the spaces 94 and the channel
102 that define the electrical lines 86, guard lines 87 and the
tongue 98.
With respect to both the spaces 94 and the channel 102, metal from
the third layer 114 is completely removed by the etching process
leaving the second layer 110 exposed through the spaces 94 or the
channel 102. The channel 118 is also formed by chemical etching.
The channel 118 has a tapered shape (i.e. it is wider at its bottom
then it is adjacent to the second layer 110) because of the etching
process. When a thick layer of metal, such as the layer 106 is
etched, the resulting groove typically has a slight tapered
shape.
FIG. 5 is a schematic diagram of a magnetic recording disk file 120
that utilizes the slider suspension systems 10 or 70 of the present
invention. It should be appreciated that the suspension systems 10
and 70 could also be used with other data storage systems that
require a vibration minimizing transducer suspension system, such
as floppy disk drives, optical drives or compact disk players.
The disk file 120 comprises a plurality of magnetic recording disks
124 suitable for use in hard disk drives. The disks 124 are mounted
on a spindle shaft 128 which is connected to a spindle motor 130.
Motor 130 is mounted to a chassis 131.
The plurality of read/write sliders 35 are positioned over the
disks 124 such that each disk 124 can be accessed by one of the
sliders 35. Each of the sliders 35 includes a transducer for
reading and writing data on a plurality of concentric data tracks
on the disks 124 and are attached to one of the suspension systems
10 (or 70). Each of the suspension systems 10 (or 70) are attached
to an actuator arm 136 which is attached to a rotary actuator 140.
The rotary actuator 140 moves the actuator arm 136 (and hence the
suspension system 10 or 70 and the slider 35) in a radial direction
across the disk 124. An enclosure 144 (shown by a dashed line in
FIG. 5) seals the disk file 120 and provides protection from
particulate contamination.
A controller unit 148 provides overall control to the system 120.
The controller unit 148 contains a central processing unit (CPU),
memory unit and other digital circuitry and is connected to an
actuator control/drive unit 152 which in turn is electrically
connected to the actuator 140. This allows the controller 148 to
control the movement of the sliders 35 over the disks 124. The
controller 148 is electrically connected to a read/write channel
156 which in turn is electrically connected to the sliders 35. This
allows the controller 148 to send and receive data from the disks
124. The controller 148 is electrically connected to a spindle
control/drive unit 160 which in turn is electrically connected to
the spindle motor 130. This allows the controller 148 to control
the rotation of the disks 124. A host system 164, which is
typically a computer system, is electrically connected to the
controller unit 148. The host system 164 may send digital data to
the controller 148 to be stored on the disks 124, or may request
that digital data be read from the disks 124 and sent to the system
164. The basic operation and structure of data storage systems,
such as the disk file 120 (without the suspension systems 10 or
70), is well-known in the art and is described in more detail in
Magnetic Recording Handbook, C. Dennis Mee and Eric D. Daniel,
McGraw-Hill Book Company (1990).
Referring now to FIG. 5, the problem addressed by the present
invention can be explained. The vibration of the arms 136 and the
suspension system 10 (or 70) in the disk file 120 produces the
undesirable effect of increasing the nonrepeatable run out (NRRO)
of the recording element of the sliders 35. This effect limits the
track density and capacity of the disk file 120.
In the disk file 120, the vibration of the arms 136 and suspension
system 10 is excited by the vibration of the disk spindle 128, the
motion of the actuator 140 and particularly the air flow inside the
enclosure 144. The amplitude of the vibration and, therefore, the
NRRO amplitude, is proportional to the degree of excitation.
Additionally, the frequency content of the excitation source is of
importance. If an excitation frequency is close to a suspension
assembly natural frequency, the amplitude of vibration will be
inversely proportional to the amount of damping. A system with very
small damping in a particular mode will have a large amplitude if
some driving frequency lies close to its natural frequency. Usually
the air flow excites all frequencies of the suspension 10 (or 70).
Then, to lower the NRRO, it is desirable to have high damping
particularly in the modes that have significant contribution the
NRRO. It is also desirable to have a design with high natural
frequencies and rigidity, with low coupling between the suspension
and slider motion and less sensitivity to the excitation
source.
Referring now to FIGS. 1 and 2, the functioning of the preferred
embodiment of the present invention can be explained. The
suspension system 10 is comprised of the three layers 50, 54 and
58. The first layer 50 is a stiffener layer that gives rigidity to
the system 10 and is the structure that needs to be damped. The
second layer 54 is a constrained layer that is constrained by the
third layer 58. The second layer 54 is comprised of a polyimide
dielectric material that functions as an electrical insulator
between the first layer 50 and the third layer 58, and that also
has viscoelastic properties. Viscoelastic means that the stress in
a deformed material is proportional to both the deformation and the
rate of deformation. Viscoelastic materials also exhibit creep and
relaxation behavior. Creep means that under constant stress the
deformation increases in time. Relaxation means that under constant
fixed deformation the stress decreases steadily in time.
The third layer 58 is comprised of an electrically conducting
material, such as a high strength copper alloy like beryllium
copper. The third layer 58 is preferably comprised of copper
because the electrical lines 26 need to function as efficient
electrical conductors. The alloy is preferably high strength
because the high modulus provides high stiffness which enhances the
constraining layer's ability to transfer strain energy into the
second layer 54. Also, the hinges 36 and 37 carry the preload
applied to the slider 35 and thus undergo high stress.
Additionally, such alloys are more stable under stress which means
preload is not lost.
The pattern of the land areas 38 and 43 and the spaces 40, 41, 44
and 45 functions to dampen the bending modes of the suspension
system 10 by providing regions in which the second layer 54 can
undergo shear. When the suspension system 10 undergoes bending
vibrations, the material of the first layer 50 undergoes cyclic
deformation. Since the second layer 54 is bonded to the first layer
50, this deformation is transmitted into the bottom surface of the
material comprising the second layer 54.
In regions where the second layer 54 is covered by a land area 38,
the top surface of the second layer 54 is constrained from
deforming beyond what the stiffness of land area 38 allows.
Therefore, layer 54 is sheared across its thickness. Shear motion
inside the layer 54 absorbs energy of the system thereby damping
the modal motion of the suspension system.
The function of the spaces 40 and 44 is to maintain the width "c"
of the land areas 38 and 43 at some optimum value. For example, if
the spaces 40 and 44 did not exist, the width "c" would be large
and the land areas 38 and 43, respectively, would become too
flexible to function efficiently as a constraining layer. On the
other hand, if the width "c" of the land areas 38 and 43 is too
narrow, the region covered by these land areas would be small and
no constraining effect would exist. In either case, less damping
would occur. Basically, the width "b" of the spaces 40 is chosen to
be as narrow as possible while still maintaining a discrete
separation between adjacent land areas 38.
The "zebra" pattern of land areas 38 depicted in FIG. 1 is aimed at
damping the bending and torsional modes of the suspension system
10. To damp these modes, some of the land areas 38 are positioned
about the axis 47 which runs perpendicular to the curvature of the
land areas 38, and passes close to one of the hinges 36. This
orientation presents the optimized land width "c" to the maximum
amount of deformation.
In the land areas 38 and 43, the width "c" is optimized to produce
the highest damping. If the width "c" is too large, the land areas
38 will be stretched by the second layer 54. On the other hand, if
the width "c" is too small, very little of the second layer 54 will
be constrained. In either of these cases, the amount of damping
obtained will be smaller than is possible with some optimized value
for the width "c."
An approximate technique for determining an optimum value for the
width "c" utilizes equation 1 below where E.sub.s =elastic modulus
of copper=1.279.times.10.sup.8 ; E.sub.1 =viscous modulus of
polyimide=1.2.times.10.sup.6 ; x=second layer thickness=0.006 mm;
y=third layer width=0.0127 mm; and .nu.=Poisson modulus of
polyimide=0.34: ##EQU1##
Once an approximate value for the width "c" has been calculated,
the width "c" can be optimized by constructing prototype systems 10
and measuring the amount of damping obtained for various
configurations. Generally, the width "c" is in the range of 0.1 to
0.8 mm.
Referring to FIGS. 1 and 5, the pair of hinges 36 are provided
between the arm portion 18 and the link portion 22 to allow link
portion 22 to pivot around axis 49 and thus allow the slider 35 and
the slider portion 14 to closely follow disk runout without
disturbing flying height between slider 35 and disk 124. The hinges
36 are part of the third layer 58 and are positioned along axis 49
to produce a preload on slider 35. This preload forces the slider
against the disk 124 and is balanced by the air bearing force
produced by the rotation of disk spindle 128 that tends to separate
the slider 35 from the disk 124. The portions of the electrical
lines 26 and guard lines 25 located between the hinges 36 and arm
portion 18 and link portion 22 is flexible enough so that they do
not affect the angle of hinges 36. Furthermore, the bending
stiffness of the link portion 22 around the axis 49 depends mostly
on the hinges 36.
The hinge 37 allows the slider portion 14 to pitch around the axis
46 and roll around the axis 51. The portions of electrical lines 26
and guard lines 25 located on both sides of hinge 37 and between
link portion 22 and slider portion 14, are flexible enough to make
the bending stiffness of the slider portion 14 around the axes 46
and 51 mostly dependent on the stiffness of hinge 37. The length
and width of hinges 36 and 37 are appropriately chosen to provide
the slider portion 14 with adequate stiffness in bending and
displacement away from its plane, thus making the slider 35 fly at
the desired flying height and keeping it as constant as possible.
Dynamic response and natural frequencies of the suspension are also
determined by the hinge stiffnesses.
Referring, to FIGS. 3 and 4, the functioning of the alternative
embodiment can be explained. During operation of a disk drive, the
bending and torsional modes of the suspension system 70 cause the
system 70 to bend and twist. However, the shape of the tongue 98
allows it to remain relatively flat during this motion, thereby
causing the part of the second layer 110 that lies under the tongue
98 to undergo stretching and shearing motions. A narrow width "f"
favors shear in the second layer 110 while a wider width "f"
produces more stretching.
An approximate technique for determining an optimum value for the
length "L" utilizes equation 2 below where f=0.4 mm: ##EQU2##
Once an approximate value for the length "L" has been calculated,
"L" can be optimized by constructing prototype systems 70 and
measuring the amount of damping obtained for various configurations
to yield an optimized value. Generally, a short length "L" will
produce little damping, but a longer length "L" will deteriorate
the suspension dynamics of the system 70.
The V-shape of the tongue 98 is chosen because this will minimize
the reduction in stiffness in the suspension system 70 while giving
maximum stiffness to the tongue 98. The maximum stiffness in the
tongue 98 and suspension system 70 is achieved when each of these
elements have the widest base possible.
Although the present invention has been described in terms of the
presently preferred embodiment, it is to be understood that such
disclosure is not to be interpreted as limiting. Various
alterations and modifications will no doubt become apparent to
those skilled in the art after having read the above disclosure.
Accordingly, it is intended that the appended claims be interpreted
as covering all alterations and modifications as fall within the
true spirit and scope of the invention.
* * * * *